Natural
but cultivated pearl produced by a mollusk after the intentional
introduction of a foreign object inside the creature's shell.
The discovery that such pearls could be cultivated in freshwater
mussels is said to have been made in 13th-century China, and
the Chinese have been adept for hundreds of years at cultivating
pearls by opening the mussel's shell and inserting into it small
pellets of mud or tiny bosses of wood, bone, or metal and returning
the mussel to its bed for about three years to await the maturation
of a pearl formation.